46 lines
1.8 KiB
Plaintext
46 lines
1.8 KiB
Plaintext
= Oscillator =
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An oscillator produces signal at a set frequency. They are useful for creating
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the base signals upon which modulation can be performed to encode information.
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An Oscillator is also known as a Clock.
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Often osciallators are created using an amplifier and a feeback circuit to
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route some of the amplifiers output signal back into its input. To make this
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oscialator produce a single frequency output, the feedback circuit must include
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a filter so feedback is present only in the intended frequency.
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Any oscillator's frequency can be variable or fixed.
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== Fixed frequency ==
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=== RC ===
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An RC oscialltor's feedback circuit is made up of Resistors (R) and Capactiors
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(C). Because of the combination of reacrance and resistance, the RC circuit
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shifts the phase of the feedback circuit so that the resulting signal, when
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amplified, reinforces the original signal
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=== LC ===
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An LC oscialltor is made up of an inductor(L) and Capacitor(C) connected in
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parallel or series to create a resonant circuit. This is sometimes called a
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tank circuit, as it stores electrical engergy, similar to a flywheel with
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mechanical energy. LC oscialltors are more stable than RC and can be used with
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a wider range of frequencies.
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=== Crystal ===
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A quartz crystal with a voltage applied creates a steady frequency that can be
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used as an osciallator, this is fare more accurate than an LC circuit.
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== Variable ==
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A Variable Frequency Osciallator (VFO) whose frequency can be adjusted, is
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used in adjustable tuners for radios. The frequency is alterted by changing the
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value of one or more components in a feedback circuit. A VFO is often made by
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having a variable capactior in an LC circuit.
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Other Variable Oscillators include a Phase Locked Loop (PLL) oscillator and a
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Direct Digital Syntehsizer (DDS). The accuracy of a DDS is comparable to a
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crystal
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